char *replaceDigits(char *s)
{
    for (int i = 0; s[i] != '\0' && s[i + 1] != '\0'; i += 2)
    { // 为了规避字符串长度为奇数的情况
        s[i + 1] = s[i] + (s[i + 1] - '0');
    }
    return s;
}